Unit 1.8 Database and Data Modelling - Database and Data Modelling Database Management Systems(DBMS File Based System \u2022 Long ago there were no

Unit 1.8 Database and Data Modelling - Database and...

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Database and Data Modelling Database Management Systems (DBMS): File Based System: Long ago there were no databases. Information was stored in “flat files” – just files full of text characters and numbers. Storing information in the flash files brought lots of problems. How do you search for a pupil? Would this be a simple operation? How easy would it be to edit the file properly? Would it be accurate, always? Searching: No index, so sequential search needed “Binary Chop” speeds things up, but still too slow And what information could be produced anyway? Search for “Andy” or “Lee” could produce lots of hits but each instance would then need to be reviewed by human for correct info. File Based systems may have no field names etc, just delimiters
Data Integrity: Data may be entered in different formats – no control No data types, no field names – no validation possible Surname or first name first? What about spaces? What about editing info – keeping them up to date? New records added but old record not removed Databases reduce the possibility of these issues Data Privacy: Different users have different needs in terms of viewing data Some data should have restricted access – both viewing and editing File based systems has no effective access control Any access control applies to the entire file, not just elements of it – granularity Only solution is to store data in several different files But this leads to data inconsistency problems. Data Redundancy: Same data stored in different files – difficult to keep up to date Data may not be updated in timely manner Data may be updated incorrectly (different standards between files) Data may not be updated at all throughout carelessness, lack of access or knowledge or communication In short, data becomes Inconsistent when stored in several places (aka Data Redundancy )

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